Method for producing a hollow handle for a teeth cleaning device

ABSTRACT

The invention relates to saucer-type handle components ( 5, 6 ) that pertain to a hollow handle and are produced in several steps. Said handle is used for a toothbrush. Said components are joined together and are inserted into an injection mould ( 25 ). A synthetic material, preferably a thermoplastic elastomer, is injection-moulded around the mould-parting line between the handle components ( 5, 6 ) in said injection mould ( 25 ). The connection seam ( 22 ) thus produced holds the two handle components ( 5, 6 ) together in a nondetachable manner and seals the hollow space ( 13 ) which is formed by the handle components ( 5, 6 ).

[0001] The present invention relates to a method for producing a hollowhandle for a teeth cleaning device, according to the precharacterizingclause of claim 1, and to a handle produced by this method.

[0002] DE-U-298 17 994.6 discloses a toothbrush in which the hollowhandle comprises two handle parts produced in separate steps, of whichat least one handle part is formed in a shell-shaped manner. The twohandle parts are welded to each other along the common parting join andare consequently connected to each other in a nondetachable manner.Adhesive bonding of the handle parts is also proposed.

[0003] A prerequisite for allowing handle parts consisting of plastic tobe correctly welded to each other is that the handle parts consist- ofweldable plastics, i.e. plastics of the same family, which restricts theselection options for the plastics to be used.

[0004] The present invention is consequently based on the object ofproviding a method of the type stated at the beginning which allowshandle parts of a wide variety of materials to be joined together toform a hollow handle and connected to each other in an nondetachable andsealed manner. This object is achieved according to the invention by thefeatures of claim 1.

[0005] The fact that, when the handle parts are joined together, theyare coated or encapsulated with a plastics material along the commonparting join by the injection-molding process has the effect that ahigh-quality sealed connection which can no longer be manually broken isobtained between the handle parts.

[0006] Preferred developments of the method according to the inventionform the subject of the dependent claims 2-12.

[0007] A handle produced by the method according to the invention isdistinguished by the features of claims 13-21.

[0008] The subject matter of the invention is explained in more detailbelow on the basis of the drawings, in which purely schematically:

[0009]FIG. 1 shows in side view a toothbrush without the brush head,with the handle parts separate from each other,

[0010]FIG. 2 shows in side view and partly in section the toothbrush puttogether from the two handle parts according to FIG. 1,

[0011]FIG. 3 shows a section along the line III-III in FIG. 2,

[0012]FIGS. 4 and 5 show the injection mold for producing the connectionseam between the handle parts,

[0013]FIG. 6 shows a cross section through the handle comprising the twojoined-together and interconnected handle parts,

[0014]FIG. 7 shows in a representation corresponding to FIG. 6 but on anenlarged scale another form of the connection between the handle parts,

[0015]FIG. 8 shows in a representation corresponding to FIG. 7 a furtherform of the connection between the handle parts,

[0016]FIG. 9 shows in side view and in a representation corresponding toFIG. 1 another embodiment of a toothbrush before the handle parts arejoined together,

[0017]FIG. 10 shows in side view the toothbrush according to FIG. 8 inthe assembled state, and

[0018]FIG. 11 shows the injection mold for producing the handle partsand the connection seam.

[0019] Firstly, the construction of a teeth cleaning device producedaccording to the invention, that is an electrically operated toothbrush1, is described on the basis of FIGS. 1-3.

[0020] The toothbrush 1 has a handle 2, which merges with a neck 3, towhich a brush head 4 is attached. The handle 2 comprises two handleparts 5 and 6, of which at least the handle part 5 and preferably alsothe handle part 6 is formed in a shell-shaped manner. The neck 3 isformed by two neck parts 7, 8, which are formed in one piece with theassigned handle parts 5 and 6, respectively. The two neck parts 7 a, 8 aare likewise formed in a shell-shaped manner. The brush head 4 (FIG. 2)has a bristle carrier 9, from which clusters of bristles 10 protrude ina known way. The bristle carrier 9 is detachably mounted on acontinuation 11 of the neck part 8. In the case of the present exemplaryembodiment, the brush head 4 is consequently exchangeable. It goeswithout saying that it is also possible to form the bristle carrier 9 inone piece with the neck part 8, which in this case means that the brushhead 4 is not exchangeable. Provided at the rear end of the handle 2 isa closure cap 12, which closes off a cavity 13 defined by the twoshell-shaped handle parts 5 and 6. The closure cap 12 in the presentexemplary embodiment is secured by means of a bayonet fastener. However,it is also possible, for example, for the closure cap 12 to be designedin such a way that it can be screwed on.

[0021] The hollow space 13 defined by the handle and neck parts 5, 6, 7,8 is divided by a transverse wall 14, molded onto the handle part 5,into a rear hollow space 13 a and a front hollow space 13 b. In FIG. 2,15 denotes a detent groove which is provided on the inner side of thehandle parts 5, 6 and belongs to the mentioned bayonet connection, bymeans of which the closure 12 is detachably secured to the handle 2. Therear hollow space 13 a serves for receiving a battery (not represented),which is supported at one end on the closure cap 12 and at the other endon a contact spring 16, which is attached to the transverse wall 14.Accommodated in the neck 3 is a micro-motor 17, which is connected to avibration element 18, for example an oscillating armature, which servesthe purpose of making the brush head 4 vibrate. The micro-motor isconnected to one terminal of the battery in the rear hollow space 13 aby means of an electrical connecting line 19 via the closure cap 12. Afurther connecting line 20 connects the micro-motor 17 to a manuallyactuable switch 21, which is provided in the handle part 5 and isconnected via a connecting line 20′ to the contact spring 16, which isin contact with the other terminal of the battery. By actuating theswitch 21, the micro-motor 17 is switched on and off. For securing orpositioning the various electrical and mechanical parts of the drive forthe brush head 4, positioning or holding parts, such as for example thetransverse wall 14, are provided on at least one handle or neck part 5,7 or 6, 8. The handle 2 and the neck 3 preferably consist of the samematerial and either of the same plastic as the bristle carrier 9 or of adifferent kind of plastic. The handle and neck parts 5, 7 and 6, 8 arepreferably produced by a one-component or multi-componentinjection-molding process.

[0022] As FIGS. 1 and 2 reveal, the handle and neck parts 5, 7 and 6, 8are produced in separate steps and then joined together. In this case,the end faces 5 a, 7 a and 6 a, 8 a of the parts 5, 7 and 6, 8 lyingagainst one another form a parting join, which is closed by means of aconnection seam 22 (FIG. 3) in a way still to be described.

[0023] The method for producing a toothbrush of the type shown in FIGS.1-3 is now described on the basis of FIGS. 4-6.

[0024] The handle parts 5, 6 produced as mentioned in separate steps andfor example at spatially separate locations, with molded-on neck parts 7and 8, respectively, are joined together to form the finished handle 2with neck 3. The handle parts 5, 6 joined together and possibly heldtogether by additional mechanical means are then placed into aninjection mold 25, such as that represented in FIG. 4. Of this injectionmold 25, the two mold halves 26 and 27 are represented purelyschematically. 28 denotes an injection opening provided in the uppermold half 26. The mutually facing end faces 5 a and 6 a and also the endfaces 7 a, 8 a of the neck parts 7 and 8 define a parting join 30. Afterthe closing of the injection mold 25, i.e. the bringing together of thetwo mold halves 26, 27, a plastics material is injected by means of anonly schematically represented injection unit 29 into the mold cavity ofthe injection mold 25 (FIG. 5). The injected plastics composition closesthe parting join 30 between the handle and neck parts 5, 6, 7 and 8 overits entire length or only over part of its length and then forms theconnection seam 22. In FIG. 6, the finished handle 2, removed from theinjection mold 25, is represented in cross section.

[0025] In the exemplary embodiment described, affinitive plastics areused for the handle and neck parts 5, 6, 7 and 8 and the connection seam22, i.e. plastics which enter into a material bond with one anotherduring the injection-molding operation. This is the case, for example,whenever polypropylene (PP) is used for the handle and neck parts 5, 6,7, 8 and a corresponding thermoplastic material, preferably athermoplastic elastomer, is used for the connection seam 22. Such amaterial bond is also obtained if the handle and neck parts 5, 6, 7, 8consist of SAN (styrene acrylonitrile) and a corresponding thermoplasticmaterial, for example a suitable thermoplastic elastomer, is used forforming the connection seam 22.

[0026] The method according to the invention, i.e. the closing of theparting join 30 between the handle and neck parts 5, 6, 7, 8 by theinjection-molding process has the advantage that even handle and neckparts which consist of plastics which are not affinitive with theplastic which is used for the connection seam 22 can be connected to oneanother in this way. This is the case, for example, if one handle orneck part 5, 7 consists of polypropylene (PP) and the other handle part6, 8 consists of SAN and a thermoplastic elastomer which enters into amaterial bond either with PP or SAN and not with the other plastic isused for forming the connection seam 22. In such cases, no material bondis produced between the parts, requiring a different configuration ofthe connection seam and/or of the handle and neck parts. Suchembodiments are now described on the basis of FIGS. 7 and 8, in which ahandle 2′ is shown in cross section.

[0027] In the case of the embodiment shown in FIG. 7, in the mutuallyfacing end faces 5 a′, 6 a′, defining the parting join 30′, there arepreferably cleat-shaped projections 31, 32, which are surrounded by theplastics material of the connection seam 22′. The projections 31, 32lying opposite one another form a hollow space 33, into which theinjected plastics composition can penetrate. In FIG. 7, the part of theconnection seam 22′ lying in this space 33 is denoted by 34.

[0028] This formation provides a mechanical, i.e. positive andnonpositive, connection between the handle parts 5′ and 6′ and theconnection seam 22′. It goes without saying that the positive ornonpositive connection between the handle parts 5′, 6′ and theconnection seam 22′ can also be produced in some other way, for exampleby providing depressions in the end faces 5 a′ and 6 a′ of the handleparts 5′, 6′, which are then filled with the plastics material of theconnection seam 22′.

[0029] In the case of the exemplary embodiment according to FIG. 8,alongside the parting join 30′ in the two handle parts 5′, 6′ there arerecesses 35 and 36, which are filled with the plastics material of theconnection seam 22′. In this case, the parts 22 a′, 22 b′ of theconnection seam 22′ lying in these recesses 35, 36 grip behindcleat-like projections 37 and 38, respectively, of the handle parts 5′,6′. The recesses 35, 36 lying respectively opposite one another in thehandle parts 5′, 6′ are respectively connected to one another over partof the length of the parting join 30′ by means of apertures 39, whichare filled with the plastics material of the connection seam 22′. Forholding together the joined-together handle parts 5′, 6′ before coatingalong the parting join 30′, in the region of the mutually facing endfaces 5 a′, 6 a′ of the handle parts 5′, 6′ there are mechanicalcentering or holding arrangements 40, which in the exemplary embodimentaccording to FIG. 8 are formed in the manner of tongue-and-grooveconnections. Preferably associated with these tongue-and-grooveconnections are cleat-like projections in one handle part 5′, whichengage in equally and oppositely formed grooves in the other handle part6′.

[0030] A mechanical connection of this type between the handle parts 5′,6′ also makes it possible to produce one handle part or both handleparts from a material other than plastic, for example from a metal, suchas for example nonferrous metal or aluminum, or even from wood.

[0031] The method explained on the basis of FIGS. 4-7 also allowstoothbrushes designed differently than the toothbrush according to FIGS.1-3 to be produced, as now explained by way of example with reference toFIGS. 9 and 10.

[0032] The toothbrush 41 shown in these FIGS. 9 and 10 comprises ahandle 42, a neck 43 and a brush head 44. The latter has a bristlecarrier 44 a, which is in one piece with the neck 43 and is providedwith clusters of bristles 44 b. The handle 42 comprises an upper handlepart 45, formed in a shell-shaped manner, and a lower handle part 46,which is in one piece with the neck 43 and may also be formed in ashell-shaped manner. The two handle parts 45, 46 define a hollow space47. After the joining together of the two handle parts 45, 48, theparting join is closed as already described by means of a plasticsmaterial in the injection-molding process. The connection seam formedthereby is denoted by 48 (FIG. 9). The two handle parts 45, 46 arepositioned with respect to each other and held together by mechanicalmeans before the coating of the parting join with the plastics material.For this purpose, the upper handle part 45 is provided with downwardlyprotruding, pinlike lugs 49, which engage in openings 50 provided in thelower handle part 46 when the handle parts 45, 46 are joined together.

[0033] The two handle parts 45, 46 are produced in separate steps. Ifthe handle parts 45, 46 consist of plastic, they are preferably producedby the one-component or multi-component injection-molding process.

[0034] After the joining together of the handle parts 45, 46, the handle42 is coated by a plastics material in an injection mold in the regionof the parting join between the handle parts 45, 46, as has beenexplained on the basis of FIGS. 4-6.

[0035] In the case of the exemplary embodiments described above, thehandle parts 5, 6, 45, 46 are produced in separate locations from oneanother, preferably by the injection-molding process, are subsequentlyjoined together and are then encapsulated along the parting join 30 withthe plastics material of the connection seam 22, 48 in a furtherinjection-molding operation.

[0036] It is also conceivable, however, to perform certain steps amongthese at the same location. For example, firstly a first handle part maybe produced. A second handle part is produced in a two-componentinjection mold and remains in this injection mold. The first handle partis joined together with the second handle part in the injection mold,for example with the aid of a robot. Then the forming of the connectionseam takes place in this two-component injection mold, possibly afterthe joined-together handle parts have been transferred into a furthercavity of the injection mold, for example by means of a robot, byinjecting the corresponding plastics material. It is also possible tobring the second handle part into the further cavity, then join thefirst handle part together with the second handle part, and after thatform the connection seam by injecting the corresponding plasticsmaterial into this further cavity.

[0037] The production of the two handle parts and of the connection seammay also take place at the same location, i.e. in a multi-componentinjection-molding installation, which is explained on the basis of FIG.11.

[0038]FIG. 11 shows in the same representation as FIGS. 4 and 5 the twomold halves 26′ and 27′ of a three-component injection mold 25′. In afirst cavity 52, the first handle part 5 is produced—with the injectionmold 25′ closed—by injecting the corresponding plastics material bymeans of the assigned injection unit 29. At the same time, in a secondcavity 52′ of the injection mold 25′, the second handle part 6 isproduced by injecting another plastics material by means of the assignedinjection unit 29. Finally, likewise at the same time, in a third cavity52″ of the injection mold 25′, the connection seam 22 is formed betweenthe handle parts 5 and 6, produced in a preceding injection cycle andthen joined together, by injecting a further different plastics materialby means of the assigned injection unit 29.

[0039]54 denotes a robot arm, having suction heads 56 for the handleparts 5, 6 and the toothbrush 1. With the mold halves 26′, 27′ separatedfrom each other after an injection operation, the suction heads 56,which can be connected to a vacuum source, simultaneously grasp the twohandle parts 5, 6 and the toothbrush 1 and lift them out of thecorresponding cavities 52, 52′, 52″.

[0040] The first handle part 5 is then inserted by means of the robotarm 54 into the third cavity 52″ of the mold half 26′ and released bydeactivating the corresponding suction head 56. Subsequently, the handleparts 5, 6 are joined together, in that the robot arm 54 places thesecond handle part 6 onto the first handle part 5. By deactivating theassigned suction head 56, the second handle part 6 is released. Once therobot arm 54 has been moved out of the region of the injection mold25′—also for discharging the toothbrush 1—, the two mold halves 26′, 27′are moved toward each other, in order to close the injection mold 25′for the next injection operation.

[0041] It is also possible to join the two handle parts 5, 6 togetheroutside the injection mold 25′—for example during an injectionoperation—and then place them in the third cavity 52″. This procedure isadvantageous in particular when further parts are to be introduced intothe cavity 13 or one of the handle parts 5, 6 is to be provided with asurface finish or be printed on.

[0042] It should be mentioned for the sake of completeness that it is ofcourse also possible to feed more than one of the cavities 52, 52′, 52″by means of a common injection unit 29. This is so if the handle parts5, 6 consist of the same plastics material, or the plastics material forthe connection seam 22 is also used for producing a membrane on one orboth handle parts 5, 6.

[0043] It goes without saying that the injection mold 25′ may have anumber of rows of first, second and third cavities 52, 52′, 52″ for thesimultaneous production of a number of toothbrushes 1.

[0044] As described, preferably a soft plastic, i.e. a plastic whichremains elastomeric, with a Shore hardness of preferably 10-70, is usedfor the forming of the connection seam 22, 48. However, it is alsopossible to use a hard plastic in the same way as for the handle andneck parts.

[0045] At least the upper handle part 5 or 44 may be opaque entirely orin certain regions or transparent entirely or in certain parts.

[0046] The hollow space 13, 47 in the handle 2, 42 may be filled with aliquid and/or items. In the case of toothbrushes, as they are shown inFIGS. 8 and 9, the filling of the hollow space takes place before theinjection-molding of the connection seam.

[0047] The fact that the connection seam 22, 48 consists of plasticallows the connection seam also to be used as an element in the visualdesign, by choosing the color of the plastic.

[0048] In the same injection-molding operation in which the plasticsmaterial for the connection seam is injected, other regions of thehandle, of the neck or of the brush head, for example the finger restingregion or sealing elements, may also be formed from this plasticsmaterial.

Patent claims
 1. A method for producing a hollow handle (2; 41) for ateeth cleaning device (1; 41), in which at least two handle parts (5, 6;45, 46) produced in separate steps, of which at least one handle part(5; 45) is formed in a shell-shaped manner, are joined together andconnected to each other along the common parting join (30),characterized in that, for producing a sealed and nondetachableconnection between the handle parts (5, 6; 45, 46), the joined-togetherhandle parts (5, 6; 45, 46) are coated with a plastics material along atleast part of the common parting join (30) by the injection-moldingprocess.
 2. The method as claimed in claim 1, characterized in that thehandle parts (5, 6; 45, 46) produced at separate locations from eachother are joined together and placed into an injection mold (35), inwhich the handle parts (5, 6; 45, 46) are coated with a plasticsmaterial along at least part of the common parting join (30).
 3. Themethod as claimed in claim 1 or 2, characterized in that handle parts(5, 6; 45, 46) consisting of plastic are used.
 4. The method as claimedin claim 3, characterized in that the production of the handle parts (5,6; 45, 46) and the coating of the parting join (30) take place indifferent cavities (52, 52′, 52″) in a single injection mold (25′). 5.The method as claimed in claim 1 or 2, characterized in that one handlepart is produced at least partly from a material other than plastic, forexample of metal.
 6. The method as claimed in one of claims 1-5,characterized in that a preferably elastomeric thermoplastic material isused for the closing of the parting join (30).
 7. The method as claimedin claims 3 and 6, characterized in that plastics which enter into amaterial bond with the plastics material of the parting join (30) areused for the handle parts (5, 6; 45, 46).
 8. The method as claimed inone of claims 1-7, characterized in that the handle parts (5′, 6′) areformed in the region of the parting join (30′) in such a way that theyare positively connected to each other by means of the connection seam(22′) consisting of the encapsulating plastic.
 9. The method as claimedin one of claims 1-8, characterized in that the handle parts arenonpositively connected to each other by means of the connection seamconsisting of the encapsulating plastic.
 10. The method as claimed inone of claims 1-9, characterized in that the joined-together handleparts (45, 46) are mechanically held together, for example by means of aplug-in connection (49, 50), before the coating.
 11. The method asclaimed in one of claims 1-10, characterized in that the hollow space(13; 47) formed by the joined-together handle parts (5, 6; 45, 46) isfilled with a liquid and/or items.
 12. The method as claimed in one ofclaims 1-11, characterized in that on the end faces (5 a′, 6 a′) of thehandle parts (5′, 6′) directed toward the parting join (30) there areformed projections (31, 32) or depressions, which are encapsulated withthe plastics material or into which the plastics material isinjection-molded.
 13. A hollow handle (2; 41) for a teeth cleaningdevice (1; 41), in particular which can be produced by the methodaccording to one or more of claims 1-12, which comprises at least twohandle parts (5, 6; 45, 46) produced in separate steps and joinedtogether, of which at least one handle part (5; 45) is formed in ashell-shaped manner, which parts are connected to each other along acommon parting join (30), characterized in that the sealed andnondetachable connection is formed by a connection seam (22; 48) ofplastics material extending along at least part of the common partingjoin (30) and produced by an injection-molding process.
 14. The handleas claimed in claim 13, characterized in that the connection seam (22;48) consists of a thermoplastic material.
 15. The handle as claimed inclaim 13 or 14, characterized in that the handle parts (5, 6; 45, 46)consist of plastic.
 16. The handle as claimed in claim 13 or 14,characterized in that at least one handle part consists at least partlyof metal.
 17. The handle as claimed in one of claims 13-16,characterized in that at least one handle part is opaque at least incertain regions or transparent completely or in certain parts.
 18. Thehandle as claimed in one of claims 13-17, characterized in that thehandle parts (45, 46) are additionally mechanically connected to eachother, preferably by means of a plug-in connection (49, 50) which iseffective before the forming of the connection seam (22).
 19. The handleas claimed in one of claims 13-18, characterized in that the hollowspace (13; 47) formed by the handle parts (5, 6; 45, 46) is filled withliquid and/or items.
 20. The handle as claimed in one of claims 13-18for an electrically operated toothbrush (1), characterized in thatelements (16, 19, 20) belonging to the drive and/or a battery areaccommodated in the hollow space (13) formed by the handle parts (5, 6),positioning or holding parts (14) for these drive elements (16, 19, 20)or the battery being provided at least on one handle part (5).
 21. Thehandle as claimed in one of claims 13-20, characterized in that on theend faces (5 a′, 6 a′) of the handle parts (5′, 6′) directed toward theparting join (30) there are formed projections (31, 32) or depressions,which are surrounded by the plastics material of the connection seam(22′) or filled with the plastics material of the connection seam (22′).